In a double heterostructure junction laser, the output radiation includes transverse modes which oscillate both parallel and perpendicular to the p-n junction plane. Numerous schemes have been suggested for producing fundamental transverse mode operation in the direction perpendicular to the junction plane; e.g. Hayashi, U.S. Pat. No. 3,733,561 issued May 15, 1973 and Hakki et al, U.S. Pat. No. 3,838,359 issued Sept. 24, 1974. Various schemes have also been suggested to produce fundamental transverse mode operation parallel to the junction plane e.g., Miller, U.S. Pat. No. 3,883,821 issued May 13, 1975 and Kressel, U.S. Pat. No. 4,122,410, issued Oct. 24, 1978.
It has been established that stabilization of the lateral position of the lasing mode parallel to the p-n junction results in improved linearity of light output as a function of current. This property is quite useful because "kinks" in the light output versus current relationship are undesirable in applications involving modulation of laser intensity.
Dixon et al, Applied Physics Letters, Vol. 20, page 372 (1976) have stabilized the lateral position of the lasing mode parallel to the p-n junction in a stripe geometry double heterostructure Al.sub.x Ga.sub.1-x As laser by narrowing from 12 .mu.m to 8 .mu.m the width of the stripe geometry active region. Control of the lateral position of the transverse mode parallel to the p-n junction has also been accomplished by utilizing built in refractive index changes along the junction plane. See Aiki et al, Applied Physics Letters, 30, 649 (1977) and Yonezu et al, Japanese Journal of Applied Physics 16, 209 (1977). All of the schemes so far reported attempt to produce and stabilize a symmetric zero order transverse mode parallel to the p-n junction plane. These structures still possess optical nonlinearities to some extent, although at increased light output. These nonlinearities are related to mode distortions which cause deviations from the symmetric zero order mode parallel to the junction plane. Some of these distortions are due to a mixing or competition between the zero order symmetric mode and the first order antisymmetric mode.